1. Field of the Invention
The present invention relates to a consumable electrode type AC pulse arc welding apparatus which uses a wire of an aluminium or an aluminium alloy, and more particularly to a consumable electrode type AC pulse arc welding apparatus, which is constituted of a simple circuit, and by which an excellent bead appearance and welding workability can be obtained, even if using the wires of different materials.
2. Description of the Related Art
A consumable electrode type AC pulse arc welding is a method of welding a workpiece by alternately feeding a straight polarity welding current and a reverse polarity pulse welding current so as to generate an arc between the arc and the workpiece while feeding a wire toward the workpiece with a preset rate. At a time of this consumable electrode type pulse arc welding, when the straight polarity welding current is being applied to the wire, i.e., when the wire is in a minus energize period (hereinafter, referred to as a straight polarity arc period), a droplet is formed at a wire tip. On the other hand, when the reverse polarity pulse welding current is being applied to the wire, i.e., when the wire is in a plus energized period (hereinafter, referred to as a reverse polarity period), a pulse current is being applied to the wire, the droplet formed at the wire tip transfers to the workpiece.
In such consumable electrode type pulse arc welding, when welding the workpiece made of an aluminium or an aluminium alloy, the most suitable condition would be different, in accordance with a material of a wire to be used. Therefore, for instance, in case of conducting a welding by using a wire (hard family) made of an aluminium alloy of No. 5000 family which is mainly used in Japan, a welding apparatus suitable for this wire is selected, thereby, an excellent welding can be implemented.
However, when applying a wire (soft family) made of an aluminium of, for example, No. 1000 family, to the welding apparatus by which an excellent welding can be implemented when the wire made of an aluminium alloy of No. 5000 family is used, the following problems would occur. That is, because of an increasing occurrence amount of sputter, the appearance of the beads could be damaged. Also, as the concentration of the arc is reduced, the welding workability possibly becomes worse. These problems are mainly caused by changing the molten temperature thereof, because of the differing materials of wires.
As described above, in a conventional welding apparatus having a single circuit configuration, it can not be applied effectively for wires of different materials. Further, such problem of which a circuit within a welding apparatus could be complicated by configuring a double circuit for the wires of each materials will occur.